The ex-congressman had been the focus of a federal investigation into alleged misuse of campaign funds to pay for personal items; the investigation eventually spread to his wife, former Chicago Ald. Sandi Jackson.

NBC reported that "those with knowledge of the investigation" believe the "loose ends now deal with Jackson's wife."

More from NBC:

Mr. Jackson "would repay the government hundreds of thousands of dollars – for items like the $40,000 Rolex watch, travel expenses for a woman he described as a 'social acquaintance' and furniture purchased for his home."